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Langstone Update 16/10/20

Posted: Fri Oct 16, 2020 9:56 pm
by g4eml
I have just released another update which adds an Rx gain control setting for each band.

The new setting is accessible through the settings menu and is titled 'Rx Gain'

The default setting is 'Auto', in this mode the Pluto automatically adjusts its RF gain so that all signals within its receiver bandwidth are below the maximum allowable level. The RF bandwidth of the Pluto is quite large so even signals that are not showing on the display can cause the gain to vary. The automatic gain control starts to reduce the gain on signals exceeding about S9 +15dB on the S meter.

Selecting away from 'Auto' will switch to manual gain control and will display the Rx gain value in dB.
Selecting one click above the maximum gain value will revert to 'Auto'

The allowable range of settings depends on the frequency being received.

70-1300 MHz -1dB to 73dB
1300-4000 MHz -3dB to 71dB
4000-6000 MHz -10dB to 62dB

These values and the automatic gain behaviour are those defined by Analogue Devices as the optimised settings for the Pluto.

The 'Auto' mode is the same as has been used in previous versions and works very well. In most cases it will not be necessary to change this.

If however if you have a very strong adjacent frequency signal that keys on and off (Local packet node or repeater) you may see the receiver gain adjusting to compensate. This can cause the wanted signal to vary in level.
In that case it might be better to adjust the gain manually to a level that allows reception of the wanted signal without being affected by the stronger one.
Note however that when set manually there is no protection from overloading the A to D converter, this won't do any harm but will probably produce unexpected results.

I did consider making the RX Gain setting available directly from a button on the screen but in practice I don't think that it will be needed very often so it is probably better left in the settings menu.

Colin G4EML

Re: Langstone Update 16/10/20

Posted: Sat Oct 17, 2020 11:50 pm
by G4FKK
Hi Colin,

Today I updated Portsdown from its update menu. That appears to work although I haven't tested it thoroughly yet.

I then updated Langstone by SSHing into it and running the usual commands...


...Langstone then sprang into life - although it seemed to take longer than usual to do that - and all the new features seem to work as you describe and so far I have not seen the intermittent TX/RX switching that I've been droning on about for ages. All good so far.

I then did a power down reboot and Langstone came back to life, again rather more slowly than hitherto. Next I pressed "Exit to Portsdown" and all was still well. However, when I then try to go back to Langstone from the Portsdown menu I get the "Langstone Transceiver Loading" screen and then nothing happens. I left it for about an hour but it was clearly locked up.

I've tried a number of reboots and also changed the System Config in Portsdown to boot to Portsdown but it would appear it is now not possible to switch to Langstone from Portsdown. Previously this wasn't an issue.

Another minor thing I've noticed (which was happening before all the updates anyway), is when I'm using QO100 and come out of the SET menu, the MONI button is blank. It still works and the annotation can be retrieved by touching one of the frequency digits.

Hope some of this is useful and that I'm not the only one similarly affected - selfish I know, but I always feel such a berk when I've obviously done something uniquely stupid :?

All the best and many thanks for all your hard work,

Martin - G4FKK

Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 9:56 am
by g4eml
Hi Martin,

The run script has changed slightly but that shouldn’t have affected anything. In theory it shouldn’t be possible for it to lock up now! I will have to build a Portsdown/Langstone combination to try it. I normally use Langstone stand alone.

The issue with the moni button is one I have seen before. I will have a look at it.


Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 10:40 am
by G4FKK
Thanks for the reply Colin. My Langstone was probably a few updates behind when I updated it yesterday - as was Portsdown - so I'll try building a new card following the latest github instructions for both later today. I wonder in which sequence you would recommend building a new card? Would it be best to install Portsdown first and use its Langstone install facility or do Langstone first followed by Portsdown?

73, Martin - G4FKK

Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 11:17 am
by g4eml
I am not sure but I think Dave’s recommendation is Portsdown first.


Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 11:20 am
by G4FKK
Ok - here goes then :)

Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 12:35 pm
by G8GKQ

I have just checked Portsdown with the latest Langstone update and can't see any problems.

You do need to reboot the Pluto before switching to Langstone if you have used it in the Portsdown. The latest Portsdown version also includes a Pluto-based Signal Generator. I have found that any time that I switch between any of the 3 Pluto modes (Langstone, Portsdown DATV and Portsdown Signal Generator) I need to reboot the Pluto (from Portsdown Menu 3, Pluto Config).

Failure to reboot the Pluto can cause the problems that you are observing.


Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 12:37 pm
by g4eml
Hi Martin,

I have just tried a build of Portsdown and Langstone and can confirm I am seeing the same problem you describe.

It appears that on selecting Langstone, Dave is sending a Langstone/stop command immediately followed by a Langstone/run command. That seems to be locking up. Removing the first stop command from line 110 of rpidatv/scripts/ fixes it for now.

However I will have a look and see why running stop immediately followed by run is causing a problem. I suspect it is because stop issues a reboot command to the Pluto and that takes time to happen.


Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 12:49 pm
by G4FKK
Thanks Dave, that's interesting. I just finished my new-build SD card and things are now working much better. I suspect I jumped the gun (yet again), by reporting the issues I was seeing without thinking things through a bit better. I'm pretty sure that my previous setup must have had a slightly older version of raspios and that maybe was causing my difficulties.

I just fired up on Langstone and all was well. I then switched to Portsdown and all was well there too. I didn't try the sig gen but I did some TX'ing on 2.4GHz followed by 146.5 MHz. Switching back to Langstone appeared automatically to reboot the Pluto and then, again, all was well.

One further observation; My Pluto is modified to take a GPS locked 40MHz and yet I still have to make (slight), adjustments to the RX/TX offsets on Langstone. The Pluto reference is set to 40000000 in Portsdown's sig gen settings menu. Are there other, frequency determining oscillators and/or registers in the Pluto?

All the best and sorry for my earlier notes,

Martin - G4FKK

Re: Langstone Update 16/10/20

Posted: Sun Oct 18, 2020 1:38 pm
by g4eml
With a GPS locked Pluto the Langstone frequency should be accurate. There is an additional error introduced by the accuracy of the sound card sampling rate but that will be very small (probably only a few Hz)